Fix typo #27

Author: xxxyyyqqq12345

orbitx/physics.py

@@ -247,7 +247,7 @@ def _collision_decision(self, t, y, altitude_event):
             else:
                 self._land(e1, e2)
         elif e2.artificial:
-                self._land(e2, e1)
+            self._land(e2, e1)
         else:
             self._bounce(e1, e2)